JP-2010-532448A, JP-2010-73705A and JP-2001-221121A disclose a fuel injection controller which controls a fuel injector. Especially, JP-2001-221121A discloses that a valve-opening time of a fuel injector is detected by detecting an inflection point on a waveform of a coil current. Furthermore, these patent documents disclose that an error of a fuel injector is corrected based on the detected valve-opening time so that an accuracy of a fuel injection quantity is improved.
It is required that a fuel injector has high responsiveness. For example, when a voltage is applied to the fuel injector, the fuel injector actually opens to inject a fuel in a short period. That is, it is preferable that a valve-opening delay is short. In order to shorten the valve-opening delay, the fuel injector is driven by high voltage and large current at a beginning of valve-opening. However, it is difficult to detect a characteristic point, such as an inflection point, on the waveform of coil current in a condition where the fuel injector is driven by high voltage and large current.
In order to detect the valve-opening time, further improvements are necessary in a fuel injection controller.